The present invention is related to a system for determining the eccentric characteristics of a tube, and particularly to a system capable of measuring the wall thickness of a tube by ultrasonic devices that determine tube wall eccentricity.
When tubes are extruded or drawn, the wall thickness varies, and sometimes these variations propagate throughout the extruding or drawing process so as to result in excessive eccentricity, and thus, in a tubing product of an unacceptable quality. Therefore, it has been found desirable to determine when such eccentricity exceeds certain limits to enable correction of the process or to terminate any further production of a defective tube before further manufacturing costs are incurred and unnecessary waste occurs.
Various types of devices have been previously employed to locate defects in or measure the eccentricity of a tube, but such devices have not be entirely satisfactory. For example, certain devices have not been capable of online operation, i.e., they have not generally been capable of eccentricity determination as the tube is extruded, drawn and/or otherwise produced. In other devices used in on-line operations, the structural arrangement and/or manner of operation impose limitations on the production of the tubing.
Therefore, a need exists for an on-line system for reliably determining tube eccentricity and maximum deviation in the wall thickness at any point around the tube circumference as the tube is being extruded. Such a system can be used to reduce manufacturing costs and maintain high quality standards, without requiring changes in the manufacturing process in order to achieve this goal.